Because iron type golf clubs constitute a majority of the golf clubs within a golfer's club allotment, improving the performance characteristics of a set of irons may significantly help a golfer to perform better on a golf course. However, due to the inherent limitation of the keeping to the traditional size and shape of an iron type golf club, the design space available for improvements in iron type golf clubs can be limiting. Hence, due to the numerous hurdles that will be encountered in attempting to improve the performance of an iron type golf club head, golf club designers have constantly struggled with even incremental improvements to the performance of these iron type golf clubs.
One of the earlier attempts to improve the performance of an iron type golf club can be seen in U.S. Pat. No. 2,846,228 to Reach; wherein a cavity is created within the rear portion of the iron golf club head to provide more perimeter weighting. Perimeter weighting improves the performance of a golf club head by providing more forgiveness through minimizing twisting of the golf club during off-center hits, resulting in straighter and more accurate golf shots.
U.S. Pat. No. 4,147,349 to Jeghers shows another early attempt to improve the performance of an iron type golf club head by lowering the Center of Gravity (CG) of the iron type golf club head while maintaining the height of the iron type golf club head. Having a golf club head with a lower CG improves the performance of the golf club head by ensuring the CG location is always lower than the impact point between a golf club and a golf ball, resulting in greater distance and accuracy.
In general, to increase performance of the iron type golf club head, the CG of these iron type golf clubs are moved lower and further back of the club head. This permits the average golfer to get the ball up in the air faster and hit the ball further. Another way to improve the performance of an iron type golf club head is to increase the Moment Of Inertia (MOI) of the club head which minimizes the distance and accuracy penalties associated with off-center hits. In order to achieve a golf club with a lower CG and a higher MOI, material or mass needs to be taken from one area of the club head where it is not maximized. This material or mass that is removed can then be relocated to alternative locations such as the rear extremities that improves the CG and MOI. One of the earlier solutions to shift weight from non-optimal placement onto a more preferred location has been to take material from the face of the club, and moving that weight to the body of the golf club head. Examples of this type of arrangement is well known in the art, and can be found in U.S. Pat. No. 4,928,972 to Nakanishi et al., U.S. Pat. No. 5,967,903 to Cheng, and U.S. Pat. No. 6,045,456 to Best et al.
In addition to the above methodologies to improve the performance characteristics of an iron type golf club head, a fairly recent development in the golf club industry is to improve the COR of the golf club head. U.S. Patent Publication No. 2001/0055996 to Iwata et al. illustrates this concept by disclosing a golf club head having a front-part component with a rear-part component wherein each of the components have a cavity to create a hollow chamber within the body of the iron-type golf club head. This hollow chamber will generally create a golf club head with a higher coefficient of restitution in the range of at least 0.81 and not more than 0.95.
Hence, as it can be seen from above, despite all the advancement in golf club technology, the current art has been unable to effectively utilize the advantages of all of the performance enhancements mentioned above in an effective manner. More specifically, the current art has been unable to create an iron-type golf club head that has a lower CG location in combination with having a high COR. Creating a high performance iron-type golf club head that has a higher COR in combination with a lower CG greatly increases the ballspeed as well as the level of forgiveness of the golf club head, which are all desirable characteristics of an iron type golf club. Ultimately, it can be seen from above that there is a need in the art for an iron type golf club head that can combine all of the performance gains that were only individually achievable in the prior art to create an iron type golf club head that not only has a high COR, but also have a lowered CG location.